COMMON RAIL MANUAL PRINCIPLES OF OPERATION

Transcription

1 TM COMMON RAIL MANUAL PRINCIPLES OF OPERATION 2007 DDGX200(EN)

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3 TABLE OF CONTENTS OBJECTIVES I THE COMMON RAIL SYSTEM II CONTROL STRATEGIES III ABBREVIATIONS IV Produced and published by: Delphi France SAS Diesel Aftermarket Boulevard de l industrie Blois Cedex Tel: (+33) (0) France Fax: (+33) (0) DDGX200(EN) - Issue 1 of 09/2007 i

4 I OBJECTIVES TABLE OF CONTENTS 1.1 REDUCING NOISE REDUCING POLLUTING EMISSIONS COMBUSTION STANDARDS POLLUTANTS REDUCING FUEL CONSUMPTION INCREASING PERFORMANCE ii DDGX200(EN) - Issue 1 of 09/2007

5 THE COMMON RAIL SYSTEM II TABLE OF CONTENTS 2. SYSTEM MAKE-UP 2.1 DESCRIPTION COMMON RAIL HYDRAULIC CIRCUIT (DFP1) HP PUMP 3.1 TRANSFER PUMP DESCRIPTION OPERATING PRINCIPLE TRANSFER PUMP CHARACTERISTICS DFP1 COMMON RAIL PUMP DESCRIPTION OPERATION CHARACTERISTICS DFP3 COMMON RAIL PUMP DESCRIPTION OPERATION SPECIFICATIONS IMV OPERATION DESCRIPTION OPERATION SPECIFICATIONS Pressure limiter Venturi INJECTOR DFI 1.X 4.1 OPERATION TECHNOLOGY Valve Crosspiece Specifications DESCRIPTION OPERATING PRINCIPLE Pressure propagation Injector at rest Coil control Injection start Injection end INJECTOR OPERATION DISCHARGE THROUGH INJECTORS C2I: INJECTOR INDIVIDUAL CORRECTION Description Procedure Development: C3I Read/Write RAIL ASSEMBLY 5.1 RAIL GENERAL DDGX200(EN) - Issue 1 of 09/2007 iii

6 II THE COMMON RAIL SYSTEM TABLE OF CONTENTS RAIL CHOICE JET RAIL PRESSURE SENSOR OPERATION INSTALLATION SPECIFICATIONS HPV OPERATION DESCRIPTION OPERATION FILTER 6.1 DESCRIPTION TECHNOLOGY FILTERING OUT IMPURITIES SEPARATING OUT THE WATER AIR MANAGEMENT REHEATER (OPTION) VENTURI 7.1 DESCRIPTION OPERATION SPECIFICATIONS THE DCU 8.1 OPERATION SPECIFICATIONS iv DDGX200(EN) - Issue 1 of 09/2007

7 CONTROL STRATEGIES III TABLE OF CONTENTS 9. RAIL PRESSURE CONTROL 9.1 PRESSURE REQUEST PRESSURE CONTROL WITH IMV ALONE WITH HPV INJECTION CONTROL 10.1 PHASING THE INJECTIONS PILOT INJECTIONS MAIN INJECTION POST MAIN INJECTION TORQUE STRUCTURE INJECTION AMOUNTS PULSE DETERMINATION CYLINDER BALANCING STRATEGY POST TO POST FUEL FLOW BALANCING CLOSED BLOCK INJECTOR DETECTION ACCELEROMETER STRATEGY RE-SETTING PILOT INJECTION DETECTING CYLINDER LEAKS DETECTING AN ACCELEROMETER FAULT ELECTRICAL EFFECT CORRECTION SENSITIVITY TO BATTERY VOLTAGE SENSITIVITY TO HARNESS RESISTANCE VLC STRATEGY DDGX200(EN) - Issue 1 of 09/2007 v

8 IV ABBREVIATIONS TABLE OF CONTENTS 11. ABBREVIATIONS / DESCRIPTIONS vi DDGX200(EN) - Issue 1 of 09/2007

9 OBJECTIVES I Note: The aim of this document is to provide generic information concerning all Delphi Common Rail systems. The Common Rail injection system has been developed to do the following: Reduce noise. Reduce polluting emissions. Reduce fuel consumption. Increase performance. 1.1 REDUCING NOISE Combustion noise is the result of the rapid pressure rise in the cylinder. The violent ignition of the air/fuel mixture in the cylinder causes this pressure rise. Note: The noise from combustion is particularly loud at idling speeds and under light loading. In a diesel engine, combustion does not start immediately after the fuel has been injected into the cylinder. This delay is called the ignition delay. The increase in cylinder pressure at the time of fuel ignition causes more or less combustion noise depending on the amount of fuel actually injected. It is thus necessary to reduce ignition time to reduce combustion noise. Increasing cylinder temperature and pressure will reduce this time. There are several methods for doing this: Reducing the amounts injected Preheating Reheating supercharged air Multi-injection (Adding an injection before the main injection) Note: Preheating and multi-injection are the two most commonly used procedures. DDGX200(EN) - Issue 1 of 09/

10 I OBJECTIVES 1.2 REDUCING POLLUTING EMISSIONS COMBUSTION In comparison with a petrol engine, the air/fuel mixture in a diesel engine is far less homogeneous: Diesel injection takes place a little time before mixture ignition. Diesel engines operate principally using an excess of air. If the air amount is too small, polluting emissions increase. Note: The air/fuel coefficient commonly denoted by lambda ( ) is equal to 1 when the air/fuel mixture is stoichiometric (14,7 / 1). <1 Air deficit, rich mixture >1 Air excess, poor mixture Note: Some diesel engines are now fitted with lambda ( ) probing, mainly to correct any flowmeter and injector drift during the lifetime of the vehicle CO (Carbon Monoxide) HC (Unburnt hydrocarbons) NOx (Nitrogen oxide) Torque (N.m) Specific consumption (g/kwh) Influence of on pollutants, torque and consumption DDGX200(EN) - Issue 1 of 09/2007

11 OBJECTIVES I STANDARDS Anti-pollution standards regulate the following pollutants: Oxides of nitrogen (NOx). Particles. (PM) Carbon monoxyde (CO). Unburnt hydrocarbons (HC). Note: The standard threshold levels are expressed in grams per kilometer (g/km). These have been in force since 1992(EURO 1) and are updated every four years on average. NOx g/km 0.97 Particles g/km EURO I (1992) HC g/km CO g/km EURO II (1996) EURO III (2000) EURO IV (2005) Direct injection Indirect injection 1200 Standard levels (g/km) Emissions in g/km Euro1 Euro2 Euro3 Euro 4 Euro 5 Motorisation Diesel IDI Diesel DI Diesel Diesel Diesel Diesel HC+NOx CO PM NOx No standard No standard Note: When the Euro2 standards were adopted in 1996, restrictions on HC emissions and particles had been less severe for direct injection engines (DI) compared to indirect injection engines (IDI). The Euro5 standards are due to come into force on 1 September DDGX200(EN) - Issue 1 of 09/

12 I OBJECTIVES POLLUTANTS Oxides of nitrogen (NOx). NOx is produced from oxidation of the nitrogen in the air. This reaction only happens at very high temperatures when there is a great excess of air. To limit oxides of nitrogen emissions, a device is used that diverts part of the exhaust gas back to the inlet manifold to limit the amount of fresh air taken into the engine. This Exhaust Gas Recirculation (EGR) device regulates the amount of exhaust gas diverted back to the inlet. If this diverted amount is insufficient, the efficiency of the system has not been optimised. In the opposite situation - insufficient fresh air - there is an increase in smoke and soot along with unstable running of the engine. Using a DENOX catyliser to post-process exhaust gases can also reduce oxides of nitrogen emissions. The principle in this process is to reduce the amount of NOx molecules generated during combustion. The process produces oxygen and nitrogem molecules separately. Diesel fuel can be used as a catalyst for reducing NOx. Given this fact, a small amount of diesel is injected into the cylinder just before the cylinder exhaust valve opens. This promotes NOx emission reduction within the DENOX catalyser, and is known as post injection. PM particles Smoke and soot can be produced in the following situations: - The mixture is too rich. In this case there is insufficient air for complete combustion. This causes particles to form. - There is incomplete fuel vaporisation in the combustion chamber. The greater the size of fuel droplets, the greater the time needed to complete the vaporisation process. If this time period is too long, the central part of the droplet will not have time to vaporise. Given the very high combustion chamber temperature, the non-vaporised fuel molecules go through a cracking process. This physical phenomenon produces very hard carbon components that form soot and the other characteristic diesel engine particulates. Unburnt hydrocarbons HC Unburnt hydrocarbons HC are generated when there is a lack of local oxygen (inadequate fuel distribution) or when fuel is injected into cold areas in the combustion chamber (typically where the fuel touches the cylinder walls). A toroidal combustion chamber combined with new intake systems (swirl) and direct injection creates the following: - Very high turbulence that ensures good fuel distribution within the combustion chamber. This eliminates the fuel-rich areas that cause unburnt elements to form. - A compact combustion chamber where the walls are hot enough to prevent unburnt particles forming. Carbon monoxide CO. Its presence in the exhaust gases causes incomplete oxidation of the carbon in the diesel fuel. This incomplete oxidation is the consequence of general or local combustion in a rich mixture. If the diesel engine is running with a significant exess of air, CO emissions are reduced. It is possible to reduce the amount even more by eliminating rich zones in the combustion chamber. To do this it is necessary to optimise the internal aerodynamics of the combustion chamber to generate a very high rate of turbulence. 1-4 DDGX200(EN) - Issue 1 of 09/2007

13 OBJECTIVES I 1.3 REDUCING FUEL CONSUMPTION Consumption reduction is obtained by improving combustion control. This is done by modifying the air coefficient, injection flow, timing advance and injection pressure in relation to engine requirements across the whole operating range. In comparison with conventional injection systems, the common rail system provides a flexibility of operation that enables injection flow, timing advance, rate of introduction and injection pressure to be accurately adjusted to engine requirements for all operating conditions. DPC DPC-N flow flow ONE INJECTION Q Q time time EPIC flow Q Q time COMMON RAIL flow Q PILOT time POST Specifics of the various Delphi systems 1300 Type of injection Timing Amount injected Number of injections DPC Mechanically set Mechanically set 1 DPC-N Electronically managed Mechanically set 1 EPIC Electronically managed Electronically managed 1 COMMON RAIL Electronically managed Electronically managed 5 Direct injection also helps improve engine output by reducing the heat loss through cylinder walls. Indirect Injection / Direct Injection 1301 DDGX200(EN) - Issue 1 of 09/

14 I OBJECTIVES 1.4 INCREASING PERFORMANCE Increasing torque at low engine speeds means being able to inject a large amount of fuel at the lowest speeds. The amount injected is proportional to injection duration and pressure. Injection pressure has to be increased to increase fuel flow, since the time available for injecting fuel into the cylinder is limited Direct injection torque 250 TORQUE (N.m) Indirect injection smoke Indirect injection torque Direct injection smoke SPEED (rpm) Increasing performance DDGX200(EN) - Issue 1 of 09/2007

15 THE COMMON RAIL SYSTEM II SYSTEM MAKE-UP 2.1 DESCRIPTION The Common Rail injection system is made up of the following parts: A Transfer Pump integrated into the High Pressure pump housing. A High Pressure Pump fed by fuel at transfer pressure. It sends fuel to the rail under very high pressure. A Low Pressure Actuator named IMV (Inlet Metering Valve). This controls the amount the fuel sent to the high pressure pump depending on engine requirements. A Rail. This forms a reserve of fuel under pressure. Injectors. These spray the required quantity of fuel into the combustion chamber at the desired moment. Use A or nothing DCU (Diesel Control Unit, otherwise known as the ECU: Electronic Control Unit) that controls injection (flow, timing, multiple injection etc) and rail pressure as a function of engine operating conditions. The DCU also controls associated functions such as the exhaust gas recirculation rate (EGR), pre-heating and air conditioning. Moreover the Swap ECU <--> DCU in the vehicle - to manage driveability, for example. Options: - A High Pressure Actuator also known as the HPV (High Pressure Valve). This is fitted to the rail and monitors its prevailing pressure. - A Force-feeding pump used where the high pressure pump does not have a transfer pump. Sensors provide the needed information in real time so that the injection process can be controlled: - A rail pressure sensor. - A fuel temperature sensor. - A inlet air temperature sensor. - A inlet air pressure sensor. - A pedal sensor. - A accelerometer sensor. - A engine flywheel angular position sensor. - A phase position sensor either on camshaft or on pump pinion (as for Renault). Note: Other sensors such as the flowmeter sensor, supercharging sensor, and exchanger exit temperature sensor are generally fitted. However these are not necessary for the Common Rail system to function. DDGX200(EN) - Issue 1 of 09/

16 II THE COMMON RAIL SYSTEM SYSTEM MAKE-UP 1 IMV 6 Venturi 2 Diesel temperature sensor 7 HPV 3 High Pressure Pump (Type DFP3) 8 Rail 4 Rail pressure sensor 9 Diesel filter 5 Injector Return to tank Feed from tank Common Rail System with HPV option 2-8 DDGX200(EN) - Issue 1 of 09/2007

17 THE COMMON RAIL SYSTEM II SYSTEM MAKE-UP 2.2 COMMON RAIL HYDRAULIC CIRCUIT (DFP1) Transfer pressure regulation Low pressure actuator Pressure limiter (high pressure) Transfer pump High pressure pump Discharge valve Inlet valve Venturi Rail High pressure sensor Injector holder Recirculation filter Cold diesel recirculation Injection pressure Hot diesel recirculation Tank KEY Inlet pressure Transfer pressure Injection pressure Return pressure Internal pressure Injector return vacuum 2200 DDGX200(EN) - Issue 1 of 09/

18 II THE COMMON RAIL SYSTEM SYSTEM MAKE-UP 2-10 DDGX200(EN) - Issue 1 of 09/2007

19 THE COMMON RAIL SYSTEM II HP PUMP To describe the HP pump operating principle, it is necessary to break down the explanation into several parts: Transfer pump High pressure pump DFP1 High pressure pump DFP3 IMV Pressure limiter Note: The "transfer pump"chapter is specific to the DFP1 pump in terms of diagrams: the operating principle remains identical to that for a DFP1 or DFP3 unit. 3.1 TRANSFER PUMP DESCRIPTION The first transfer pump stage, draws diesel from the vehicle tank through the filter and sends it to the main pump under transfer pressure (about 6 bar) The blade pump technology used (well known from our preceding products) has the following parts: A rotor driven from the HP pump shaft. Torque is transferred by splined shaft. An eccentric liner fitted in the HP pump housing. Two off-set pins that locate the liner correctly and ensure correct assembly. One plate with two oblong holes: one inlet orifice and one discharge orifice. Four blades at 90 degrees to each other. Each blade is held against the liner by a coil spring OPERATING PRINCIPLE Consider the space between the rotor, the liner and two successive blades. When the chamber is in position 1, the volume of the chamber is minimal. The volume change related to rotor angular travel is insignificant in this position. The rotor makes a quarter-turn anti-clockwise. The previous chamber is now in position 4. The inlet orifice is uncovered. The volume of the chamber quickly rises. The pressure in the chamber drops sharply. Fuel is drawn into the chamber. The rotor continues to rotate. It is now in position 3. Inlet and outlet orifices are now sealed off. The volume contained by the rotor, liner and the two blades is now at a maximum. Any changes in volume that depend on the rotor angle of rotation are small. Transmission shaft Blade Inlet pressure 3 Transfer pressure 3110 The rotor continues to rotate. It is finally in position 2. The outlet orifice is uncovered. The volume contained by the rotor, liner and the blades diminishes rapidly. The pressure in this space increases sharply. The fuel is discharged under pressure. DDGX200(EN) - Issue 1 of 09/

20 II THE COMMON RAIL SYSTEM HP PUMP The vacuum generated by the transfer pump rotation is enough to draw in fuel through the filter. The transfer pump is driven by the HP pump shaft. Transfer pressure thus rises with engine speed. A regulating valve maintains transfer pressure at a quasi constant value (about 6 bar) throughout the engine operating range by sending part of the fuel back to pump inlet. Pressure (bar) Pump speed (rpm) 3120 Transfer pressure TRANSFER PUMP CHARACTERISTICS Regulating pressure 6 bar Flow: 90 l/h at 300 rpm Output 650 l/h at 2500 rpm Swept volume 5.6 cm 3 /rev. Intake capacity 65 mbar at 100 rpm Inlet Transfer pump with its pressure regulator 3130 The transfer pressure regulator mechanically controls transfer pressure using a single piston/ spring arrangement to cover and uncover the fuel flow orifices. As can be seen on the preceding diagram, the output from the regulator is recycled to the transfer pump inlet Close-up on transfer pressure regulator section 3-12 DDGX200(EN) - Issue 1 of 09/2007

21 THE COMMON RAIL SYSTEM II HP PUMP 3.2 DFP1 COMMON RAIL PUMP DESCRIPTION This high pressure pump uses the cam and radial piston concept already proven on the DPC and EPIC rotating pumps. However the transmission shaft and cam ring make up the one and same assembly. This is driven by chain or belt, rotating in the fixed hydraulic head. This design eliminates dynamic sealing problems since the high pressure is generated in the fixed part of the pump. For engines needing substantial flow rates, the pump is fitted with two chambers angularly offset by 45 degrees. This offset reduces torque peaks and rail pressure variations. The four-lobe cam is identical to that in conventional rotating pumps. However since the pump no longer determines injection procedure, it is possible to lengthen the pumping phase in order significantly to reduce driving torque, vibration and noise. DFP1 High Pressure Pump IMV 6 Roller 2 High pressure pump / Hydraulic head 7 Transfer pump 3 Plunger Piston 8 Diesel temperature sensor 4 Drive transmission shaft 9 High Pressure Exit 5 Rotary cam DFP1 High Pressure Pump section view DDGX200(EN) - Issue 1 of 09/

22 II THE COMMON RAIL SYSTEM HP PUMP OPERATION A) PUMP FEED The transfer pump draws fuel through the filter. This delivers fuel to the HP pump entry point at a quasi-constant pressure known as the transfer pressure. A filling actuator is fitted upstream of the HP pump. This controls the amount of fuel sent to the pumping system by adjusting the (Inlet Metering Valve IMV) cross-section of the flow path. The ECU determines the coil current to set the flow path cross-section required to achieve the requested pressure for the engine operating conditions. When the requested pressure reduces the current increases, and vice-versa. 1 Hydraulic head body 3 Inlet valve 2 Roller shoe 4 Outlet valve DDGX200(EN) - Issue 1 of 09/2007

23 THE COMMON RAIL SYSTEM II HP PUMP B) PUMPING PRINCIPLE During the filling phase, two helical springs - one on each piston - keep the cam rollers in contact with the cam. The transfer pressure is sufficient to open the inlet valve and to move the plunger pistons apart. In this way the dead space between the two plunger pistons fills with fuel. When the diametrically opposite rollers simultaneously move over the cam raise profile, the pistons are pushed together. Pressure rapidly increases in the space between the two plunger. Intake phase 3221 When the pressure rises above transfer pressure the inlet valve closes. When pressure goes above rail pressure the outlet valve opens. The fluid under pressure is then delivered to the rail. Discharge phase 3222 DDGX200(EN) - Issue 1 of 09/

24 II THE COMMON RAIL SYSTEM HP PUMP C) INLET AND OUTLET VALVES In the intake phase, the transfer pressure opens the valve. Fluid enters the body of the pump element. Under the effect of the transfer pressure, the plunger pistons move apart. When the rollers simultaneously meet the cam raise profile, pressure suddenly increases in the pump element body. The valve closes when the pump element body pressure becomes greater than the transfer pressure. Inlet valve 3223 In the intake phase, the discharge valve ball comes under rail pressure on its external face and under transfer pressure on its internal face. The ball thus remains in its seating thus ensuring pump element body sealing. When the two diametrically opposite rollers simultaneously meet the cam raise profiles, the plunger pistons move towards each other and the pump element body pressure rapidly increases. When the pressure in this element becomes greater than rail pressure, the ball is in disequilibriuim and consquently opens (the spring loading is negligible in relation to the pressure loading) Fuel thus flows into the rail under high pressure. valve 3224 D) PUMP LUBRICATION AND COOLING The fuel in circulation keeps the pump lubricated and cooled. The mininim flow needed for pump operation is 50 litres/hour DDGX200(EN) - Issue 1 of 09/2007

25 THE COMMON RAIL SYSTEM II HP PUMP E) PUMP PHASING Conventional injection pumps distribute fuel under pressure to the various injectors. It is thus essential to phase the pump so that injection takes place at the required point in the cycle. The Common Rail system HP pump no longer distributes the fuel so it is not essential to phase the pump with the engine. However phasing the pump has two advantages: Variations in torque from the camshaft and the pump can be synchronised to limit stress on the drive belt. Pressure control can be improved by synchronising pump-produced pressure peaks with the falls in pressure generated by each injection. This phasing improves pressure stability, which helps reduce the difference in flow between cylinders (line to line). Phasing the pump will be done using a pin inserted in the pump drive shaft. Note: Phasing is obligatory on DFP1 pumps fitted on Renault applications. Unlike the practice with other car builders, the phase sensor is not positioned on the camshaft but on the pump pinion. It is therefore essential to phase the pump on Renault applications to avoid any problem with engine synchronisation CHARACTERISTICS A) DFP1 MAX PRESSURE GRAPH The time needed to achieve sufficient rail pressure to start, depends on the injection system volume (rail dimensions, tubing length, etc). The object is to achieve a 200 bar pressure in 1.5 revs (3rd compression). Rail pressure (bar) Engine speed (rpm) 3230 DDGX200(EN) - Issue 1 of 09/

26 II THE COMMON RAIL SYSTEM HP PUMP B) CHARACTERISTICS Applicatio ns Capacity (cm 3 /rev) No. of plungers Rack Ratio Max Pump Speed Max Rail pump Speed Drives Renault K / bar bar Belt PSA DV4TED / bar bar Belt Ford Puma Transit / bar bar Chain Ford Lynx/ Puma / bar bar Chain Kia / bar SsangYong / bar bar Belt Chain 3-18 DDGX200(EN) - Issue 1 of 09/2007

27 THE COMMON RAIL SYSTEM II HP PUMP 3.3 DFP3 COMMON RAIL PUMP DESCRIPTION The DFP3 high pressure pump marks a change from the DFP1 concept. The transmission drive shaft and cam assembly for this pump are replaced by a shaft with an eccentric part connected to push rods. This eccentric is rotated by the pump transmission shaft. Its specific rounded form is designed to drive the push rod movement and generate high pressure. For engines needing substantial flow rates, the pump is fitted with three plungers angularly placed at 120 degrees to each other. For engines needing a less substantial flow rate, a 2-plunger solution has been adopted, with the plungers angularly placed at 180 degrees. Since the pump no longer sets the injection procedure - in the same way as for the DFP1 - it is possible to extend the pumping phase so as to reduce drive torque, vibration and noise. The most significant differences from the DFP1 are: The eccentric The transmission shaft shape. The number of plungers. Roller bearings replaced by plain bearings. Greater pumping capacity per revolution. Higher rotation speed. Reduced pump overall dimensions. Transfer pump as an option piston DFP3 pump DDGX200(EN) - Issue 1 of 09/

28 II THE COMMON RAIL SYSTEM HP PUMP OPERATION A) PUMP FEED WITH OR WITHOUT TRANSFER PUMP A transfer pump draws diesel through the filter, or a feeder pump in the fuel tank puts the fuel under pressure. In the first case, the pumping principle employs the DFP1 transfer pump concept. See Paragraph 3.1: DFP1 Transfer pump Operation and characteristics are almost the same as for the DFP1. The only major difference is in it being placed on the front and no longer directly inside the pump housing itself. A feed pressure regulator internal to the pump is needed when using a transfer pump. 1 Transfer pump body 4 Rotor 2 Blades (x4) 5 High pressure pump body 3 Distribution plate 6 Liner Section view of optional transfer pump for DFP DDGX200(EN) - Issue 1 of 09/2007

29 THE COMMON RAIL SYSTEM II HP PUMP B) PUMPING PRINCIPLE The pump is driven by belt, chain or Oldham drive as shown in diagram below (12). The transmission torque is sent via drive shaft (13) to the eccentric, or cam (7). In the diagram the cam (7) is in rest position with its flat faces touching the push rods (6). The cam is considered to be in a working position when one of the curved faces is acting on one of the push rods. This push rod drives plunger piston (3) and compresses spring (4). The amount of fuel compressed at piston travel is represented by figure 2 on the hydraulic head diagram. 1 Cylinder head 8 Pump body 2 Discharge valve 9 Inlet valve 3 Plunger Piston 10 Cylinder head gasket 4 Piston spring 11 Identification plate 5 Spring retaining cup 12 Oldham drive 6 Push rod 13 Drive shaft 7 Cam Section view of the 3-plunger version of the DFP3 DDGX200(EN) - Issue 1 of 09/

30 II THE COMMON RAIL SYSTEM HP PUMP C) HYDRAULIC HEAD Diesel at transfer pressure goes to the hydraulic head via orifice (5) and then passes through the inlet valve. This amount of fuel is then compressed in chamber (2) at each piston rise. This amount then moves at high pressure through the outlet valve before being sent through orifice (6). This orifice is itself linked to the other HP hydraulic head exits so as to centralise all high pressure fuel Section view of a hydraulic head 3322 D) INLET AND OUTLET VALVES The opening and closing of the valves depend on the movements of the plunger pistons, as follows: In the expansion phase, the descending piston generates a vacuum that causes the inlet valve to open thus filling the compression chamber. On the return, the outlet valve remains in its seating since the actual pressure behind it is equal to the rail pressure. In the compression phase, the inlet valve closes as the rising piston puts the fuel in the chamber under pressure and thus pushes the valve into its seating. The discharge valve opens when the chamber pressure becomes greater than the rail pressure. Inlet valve Discharge valve Close-up of hydraulic head valves 3323 Note: The inlet and outlet valve springs are only there to help their movement. The loading of these springs is light and does not constitute an obstacle in terms of the pressures operating in the hydraulic head DDGX200(EN) - Issue 1 of 09/2007

31 THE COMMON RAIL SYSTEM II HP PUMP SPECIFICATIONS 1 DFP3.1 3 DFP3.3 2 DFP3.2 4 DFP Specifications DFP3.1 DFP3.2 DFP3.3 DFP3.4 Number of plungers Capacity (cm 3 /rev) 0.75 to to to to 0.7 Max pressure (bar) 1600 to to to to 2000 Drives Belt/Chain/Oldham Belt/Chain/Oldham Belt/Chain/Oldham Belt/Chain/Oldham Speed ratio in relation to engine speed 1/2 to 4/3 1/2 to 4/3 1/2 to 1 1/2 to 1 Max speed (pump rpm) Transfer pump Integrated as an option Integrated as an option Integrated as an option Integrated as an option DDGX200(EN) - Issue 1 of 09/

32 II THE COMMON RAIL SYSTEM HP PUMP Max Pressure DFP3.1 Pressure (bar) Pump speed (rpm) 3331 DFP3.1 max pressure graph 3.4 IMV OPERATION DDGX200(EN) - Issue 1 of 09/2007

33 THE COMMON RAIL SYSTEM II HP PUMP The low pressure actuator also called the Inlet Metering Valve controls rail pressure by regulating the amount of fuel sent to the pumping components of the HP pump. This actuator has a double role as follows: First it improves injection system output since the HP pump only compresses the amount of fuel needed to maintain the rail pressure required by the system. Specific consumption (g/kwh) IMV EFFECT 3500 rpm - without EGR without with Torque (N.m) Rail Pressure = 800 bar 3411 Secondly it reduces the temperature in the fuel tank. In fact when excess fuel is sent to the return circuit, the expansion of the fluid (from rail pressure to atmospheric pressure) involves a large amount of heat. This generates an increase in temperature of the fuel sent back to the tank. To avoid generating too high a temperature, it is necessary to do the following: - Cool the diesel in the exchanger (a costly, cumbersome and not very efficient solution). - Limit the amount of heat generated by fuel expansion by reducing the rate of discharge. To reduce the rate of discharge, it is enough to adapt the HP pump output to engine needs within the whole operating range. This is what the IMV does. Fuel Temperature ( C) RETURN CIRCUIT DIESEL TEMPERATURE Torque (N.m) without with DESCRIPTION The IMV is fitted to the pump hydraulic head. The transfer pump feeds fuel to it via two radial drill holes. A cylindrical filter is fitted to the IMV feed orifices. This not only protects the low pressure actuator but also protects all the injection system components downstream of the IMV. It is made up of the following elementsin Fig. 3420: DDGX200(EN) - Issue 1 of 09/